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Asynchronousflowering ofBrassica napus(canola) leads to seeds and siliques at varying stages of maturity as harvest approaches. This range of maturation can result in premature silique dehiscence (pod shattering), resulting in yield losses, which may be worsened by environmental stresses. Therefore, a goal for canola crop improvement is to reduce shattering in order to maximize yield. We performed a comprehensive transcriptome analysis on the dehiscence zone (DZ) and valve ofArabidopsisandBrassicasiliques in shatter resistant and sensitive genotypes at several developmental stages. Among knownArabidopsisdehiscence genes, we confirmed that homologs ofSHP1/2,FUL,ADPG1,NST1/3andINDwere associated with shattering inB. junceaandB. napus. We noted a correlation between reduced pectin degradation genes and shatter-resistance. Tension between lignified and non-lignified cells in the silique DZ plays a major role in dehiscence. Light microscopy revealed a smaller non-lignified separation layer in relatively shatter-resistantB. juncearelative toB. napusand this corresponded to increased expression of peroxidases involved in monolignol polymerization. Sustained repression of auxin biosynthesis, transport and signaling inB. juncearelative toB. napusmay cause differences in dehiscence zone structure and cell wall constituents. Tension on the dehiscence zone is a consequence of shrinkage and loss of flexibility in the valves, which is caused by senescence and desiccation. Reduced shattering was generally associated with upregulation of ABA signaling and down-regulation of ethylene and jasmonate signaling, corresponding to more pronounced stress responses and reduced senescence and photosynthesis. Overall, we identified 124 cell wall related genes and 103 transcription factors potentially involved in silique dehiscence. [ABSTRACT FROM AUTHOR]

This light and electron microscope study reveals considerable uniformity in hornwort stomata morphology and density in contrast to common spatial and developmental abnormalities in tracheophytes and mosses. Stomata arise from a median longitudinal division of sporophyte epidermal cells morphologically indistinguishable from their neighbours apart from the retention of a single chloroplast whilst those in the other epidermal cells fragment. Chloroplast division and side-by-side repositioning of the two daughter chloroplasts determines the division plane in the stomatal mother cell. The nascent guard cells contain giant, starch-filled chloroplasts which subsequently divide and, post aperture opening, regain their spherical shape. Accumulation of wall material over the guard cells and of wax rodlets lining the pores follows opening. While the majority of stomata are bilaterally symmetrical those lining the dehiscence furrows display dextral and sinistral asymmetry due to differential expansion of the adjacent epidermal cells. The ubiquity of open stomata suggests that these never close with the maturational wall changes rendering movement extremely unlikely. These structural limitations, a liquid-filled stage in the ontogeny of the intercellular spaces, and spores already at the tetrad stage when stomata open, suggest that their primary role is facilitating sporophyte desiccation leading to dehiscence and spore dispersal rather than gaseous exchange. Stomata ontogeny and very low densities, like those in Devonian fossils, suggest either ancient origins at a time when atmospheric carbon dioxide levels were much greater than today or a function other than gaseous exchange regulation. We found no evidence for stomatal homology between hornworts, mosses and tracheophytes. [ABSTRACT FROM AUTHOR]

Pod shattering (dehiscence) is a major constraint to soybean (Glycine max. (L) Merrill) production in the northern savanna zones of Ghana, but research on improving soybean for resistance to shattering is scanty. Genetic analysis of resistance to pod shattering was undertaken on three soybean crosses involving resistant and susceptible varieties to determine broad-sense (h2bs) and narrow-sense (h2ns) heritability, minimum number of genes (MNG) involved cytoplasmic inheritance, and allelic relationship between shattering and non-shattering. Mean h2bswas 0.92 (range 0.90–0.95), and mean h2nswas 0.46 (range 0.40–0.53), indicating the importance of both additive and non-additive variances and that shattering resistance can be improved through breeding. Mean MNG controlling shattering resistance was 2 (range 1–3), indicating that genes for shattering resistance differed among parental lines. There was no difference between the mean of any F1population and it's reciprocal, indicating lack of maternal/cytoplasmic influence and that the character was under nuclear gene control. Observed F2ratios revealed that inheritance of resistance to pod shattering in soybean was qualitative in nature and under the influence of either duplicate recessive or dominant and recessive epistasis, depending on the parental genotypes used in the cross. [ABSTRACT FROM PUBLISHER]

Information on fruit setting in teasle gourd [Momordica subangulataBlume subsp.renigera(G. Don) WJJ de Wilde] has received little attention, and the precise nature of its breeding system has never been described. A study was undertaken on the pollination mechanism, fruit setting, and interspecific and intergeneric crossability for genetic improvement of teasle gourd. The first flower produced by the male clone reached full bloom 75 days after emergence from the soil; those produced by female clones required an average of 53 days. Number of nodes producing the first flower varied from plant to plant and subsequent flowers also did not develop in any definite sequence. The time required by male and female flower buds to reach anthesis was 15 and 10 days, respectively. Opening of either type of flower occurred between 6 and 7am,and dehiscence of anthers began at time of opening of female flower. The stigma became receptive 12 hours before anthesis. No fruit set was obtained by hybridization between teasle gourd and other cucurbits, indicating little likelihood for recombination of desirable characters from others cucurbits into teasle gourd using fresh pollen. [ABSTRACT FROM AUTHOR]

A protruding oncus is a projection of the intine in the aperture region. The ubiquitous use of acetolysis in palynological research has led to the presence of a protruding oncus being underreported. Controlled experiments with pollen samples collected from undehisced and dehisced anthers demonstrate that the presence of a protruding oncus is affected by the state of the anther at maturity: dehisced or undehisced and by the preparation technique. In investigating the occurrence of onci, particular attention should be paid both to the dehiscence state of the anthers and the effect of the preparation technique on the intine. Although it has been suggested that protruding onci and pollen buds can be distinguished based on three criteria (size, presence of a large vacuole, separation of the protrusion from the grain), most of these distinctions break down when information is included from more recent studies. Additional study of protruding intinous structures may help clarifing the difference between pollen buds and protruding onci. [ABSTRACT FROM AUTHOR]

Conclusion: Testing cervical vestibular evoked myogenic potential (cVEMP) in response to 90 dB nHL clicks can, in contrast to high-intensity 500 Hz tone bursts, be used as a screening test for superior canal dehiscence (SCD) syndrome. Objectives: cVEMP testing has its key clinical significance for evaluating saccular and inferior vestibular nerve function, but also for assessment of vestibular hypersensitivity to sounds in patients with SCD syndrome. The routine stimulus used in cVEMP testing is high-intensity 500 Hz tone bursts. The aim of the present study was to compare the high-intensity tone burst stimulation with less intense click stimulations for the diagnosis of SCD syndrome. Methods: cVEMP amplitudes in response to 500 Hz tone bursts and clicks were studied in 38 patients with SCD syndrome unilaterally. Results: cVEMP testing using high-intensity 500 Hz tone bursts did not consistently distinguish SCD patients. This nonfunctioning of high-intensity 500 Hz stimulation is most likely due to saturation. With 90 and 80 dB nHL clicks there is low risk for saturation and both these click stimulations were effective. Testing with both 80 and 90 dB nHL clicks did not have any significant advantage over just using 90 nHL dB clicks. [ABSTRACT FROM AUTHOR]

We investigated the mycorrhizal associations in 31 adult wild or cultivated green orchids (22 epiphytic, 8 terrestrial, and 1 species with both epiphytic and lithophytic life-forms) from different vegetation types of Western Ghats, southern India. All the orchids examined were mycorrhizal with the extent of colonization varying with species and life-forms. Mycorrhizal association has been reported for the first time in 25 orchids. The entry of mycorrhizal fungi into the roots was mostly through root hairs. In certain epiphytic species, the fungal entry was directly through the epidermis. The fungi formed highly coiled hyphal structures (pelotons) within the root cortex, and their size was related to the cell size. The fungal invasion of the cortical cells was through cell-to-cell penetration. The cortical cells contained intact and lysed pelotons, and their ratio varied with species and life-forms. No significant relationship existed between root hair characteristics and the extent of colonization. Chlamydospores and microsclerotia-like structure were frequently found within the cortical and root hair cells. The liberation of fungal reproductive structures was by spiral dehiscence of the root hairs. [ABSTRACT FROM AUTHOR]